return user IDs (group IDs)—for example, getuid (2), getgid (2), and the credential fields ... user namespace may call getuid (2) before a user ID mapping has been definedobtain its real user (group) ID using getuid (2) ( getgid (2)). • Effective usergetppid (2) getsockname (2) getsockopt (2) getuid (2) htonl (3) Added in POSIX.1-2008 TC2 htons